The diverter valve performs a critical function within the overall operation of the boiler, being activated every time there is a demand for domestic hot water. One of the main advantages of these combination boilers is that they provide domestic hot water at mains pressure, eliminating the need for cold water tanks and shower booster pumps. The diverter valve is the component within the boiler that responds when a hot water tap is opened and diverts primary (heating) water to a heat exchanger in which the mains pressure domestic water is heated to a comfortable level.